1. Field of the Invention
This invention relates to improved hydrocarbon fuels which control the octane requirement increase (ORI) phenomenon conventionally observed during the initial portion of the operating life of spark ignition internal combustion engines.
2. Description of the Art
The octane requirement increase (ORI) effect exhibited by internal combustion engines, e.g., spark ignition engines, is well known in the art. This effect may be described as the tendency for an initially new or clean engine to require higher octane quality fuel as operating time accumulates and is coincidental with the formation of deposits in the region of the combustion chamber of the engine. Thus, during the initial operation of a new or clean engine, a gradual increase in octane requirement (OR), i.e., fuel octane number required for knock-free operation, is observed with an increasing buildup of combustion chamber deposits until a rather stable or equilibrium OR level is reached, which, in turn, seems to correspond to a point in time where the quantity of deposit accumulation on the combustion chamber and valve surfaces no longer increases but remains relatively constant. This so-called "equilibrium value" is usually reached between about 3,000 and 20,000 miles or corresponding hours of operation. The actual equilibrium value of this increase can vary with engine design and even with individual engines of the same design; however, in almost all cases the increase appears to be significant, with ORI values ranging from about 2 to 14 Research Octane Numbers (RON) being commonly observed in modern engines.
It is also known that additives may prevent or reduce deposit formation, or remove or modify formed deposits, in the combustion chamber and adjacent surfaces and hence decrease OR. Such additives are generally known as octane requirement reduction (ORR) additives.
For example, in U.S. Pat. No. 4,264,335 to Bello et al., the cerous or ceric salt of 2-ethylhexanoate is disclosed as a useful additive for suppressing the octane requirement increase of a gasoline fired internal combustion engine. It is noted in this patent that the above salt has no effect on combustion efficiency of a gasoline and does not provide anti-knock properties.
In U.S. Pat. No. 4,357,148 to Graiff there is disclosed an additive for controlling or reversing the octane requirement increase of a spark ignition internal combustion engine which comprises a combination of (a) certain oil soluble aliphatic polyamines and (b) certain low molecular weight polymers and/or copolymers of mono-olefins having up to 6 carbon atoms.
U.S. Pat. No. 3,506,416 to Patinkin et al. discloses an additive to inhibit octane requirement increase of a spark ignition engine which comprises a gasoline soluble metal salt of a hydroxamic acid. This additive is disclosed as useful in leaded gasoline. Although iron is within the broad group of metal salts of hydroxamic acid that are disclosed as a suitable additive for suppression of octane requirement increase, no data demonstrating its effectiveness are given. In fact, the patentees point out that nickel and cobalt are especially preferred for their additive.
Other references describing additives for inhibiting octane requirement increase include U.S. Pat. Nos. 3,144,311 and 3,146,203 which disclose utilization of nitrogen ring compounds in combination with organo metallic primary antiknock agent and a minor amount of an ignition control additive selected from the group consisting of phosphorus and boron compounds.
Thus, none of the references disclose the combination of an oil-soluble iron compound and a carboxylic acid or ester thereof for use in suppressing the octane requirement increase of a spark ignition internal combustion engine.
Various workers in an attempt to improve the anti-knock properties of gasolines have tested iron compounds and carboxylic acids and esters as gasoline additives. For example, U.S. Pat. No. 3,344,311 discloses that various dicyclopentadienyl iron compounds are useful as anti-knock additives for gasolines. This reference teaches that the dicyclopentadienyl iron compound in combination with tetraethyl lead provides a synergistic anti-knock additive for gasoline. Other workers have tested dicyclopentadienyl iron in combination with manganese (U.S. Pat. No. 4,139,349) and nickel (U.S. Pat. No. 3,353,938) and found that such combinations provide synergistic anti-knocking properties as compared to either individual component alone. None of these references, however, suggests the combination of dicyclopentadienyl iron with carboxylic acids or esters thereof.
Various carboxylic acids and derivatives thereof have been tested for extending the anti-knocking properties of lower alkyl lead compounds such as tetraethyl lead. See for example, `Carboxylic Acids Extend the Antiknock Effectiveness of Tetraethyl Lead,` W. L. Richardson et al., The Journal of Chemical & Engineering Data, Volume 6, No. 2, (April 1961), pages 309-312. This article suggests that tertiary butyl acetate and other efficient extenders operate by decomposing to a carboxylic acid, which combines with lead oxide during the combustion cycle to alleviate knocking properties of gasolines to which such extenders are added. It is pointed out that the optimum mole ratio of the extender to tetraethyl lead is 15, a much higher ratio than required for the iron-carboxylic acid or ester derivative disclosed in this invention. Moreover, this reference is limited to extending the anti-knock properties of alkyl lead additives and does not suggest the combination of such extenders with any other organo metallic compound.
Another reference which discusses extending the anti-knock properties of tetraalkyl lead is `Are There Substitutes For Lead Antiknocks?` G. H. Unzelman et al., AIChE Volume 22, No. 4, beginning at page 701. This reference discusses the research over a period of years to find materials that could substitute or extend the properties of alkyl lead as an anti-knocking additive for gasoline. The many compounds tested include organo iron compounds such as iron carbonyl complexes which were found to be effective anti-knocking additives. The reference also discusses using organic oxygen compounds in substantial concentrations to reduce knock. The authors point out that certain esters are lead appreciators (extenders) but note that tertiary butyl acetate is of limited interest because its effectiveness diminishes as the lead content of the gasoline is reduced. Moreover, it is pointed out that tertiary butyl acetate is not as effective if the octane level of gasoline to which it is added is reduced. This reference does not suggest the combination of an iron soluble compound with a carboxylic acid or ester derivative thereof in either leaded or unleaded gasoline.
Thus, it is one object of this invention to provide a hydrocarbon fuel containing a novel additive which suppresses the octane requirement increase of spark ignited internal combustion engines.
It is another object of the instant invention to control or reverse the octane requirement increase phenomenon in a spark ignition internal combustion engine by introducing a novel additive with the fuel.
It is another object of the instant invention to provide a liquid hydrocarbon motor fuel for spark ignited internal combustion engines containing a novel anti-knock additive.
It is another object of the instant invention to provide a lead free liquid hydrocarbon fuel containing a novel anti-knock additive and a novel additive for inhibiting the octane requirement increase of a clean internal combustion engine.
Other objects are to provide new compositions of matter and to advance the art.
Other objects and advantages of the instant invention will become apparent to those skilled in the art from the following description.